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[46P.09] High Resolution Infrared Heterodyne Spectroscopy: Ethylene bands at 10.5 \mum.

V. Morozhenko, T. Kostiuk, D. Buhl (NASA GSFC), T. Hewagama (Challenger Ctr.), T. A. Livengood (NASA GSFC /UMD), A. Kollyukh (Institute of Semiconductor Physics, UKRAINE)

Heterodyne Spectroscopy can make a significant contribution to remote studies of planetary atmospheres and other gaseous astronomical objects. Infrared heterodyne investigations of planetary atmospheres permit the determination of their composition, distribution of pressure and temperature with altitude, and the investigation of local physics and chemistry. This method is especially important for the investigation of atmospheric dynamics. It has a high spectral resolution ( \lambda/\Delta\lambda \approx 10⁷ ), which makes it possible to remotely determine the direction and speed of winds with an accuracy 2 m/s (J.Goldstein et al., 1991). However, in order to retrieve the atmospheric parameters from atmospheric line measurements, it is important to know the molecular parameters of the lines being measured. Ethylene (C₂H₄) is an important hydrocarbon present in atmospheres of Jupiter, Saturn, and Titan (e.g., T.Kostiuk et al., 1993). It is a product of methane chemistry in the stratospheres of these planets and has a complicated spectrum in the middle IR region. This makes it a very interesting and usable probe of physical-dynamical properties of these atmospheres. In this report we present initial results of laboratory investigations of absorption lines of ethylene in the \nu₄, \nu{₇} and \nu₁₀ bands near 10.5 \mum. The measurements were made using a laboratory infrared heterodyne spectrometer with the ethylene gas at temperatures 293-297K and pressures 0.05-50 Torr.

Parameters of more than 150 lines were measured relative to lines in the P and R branches of the ¹²CO₂ laser and in the P branch of the ¹⁴CO₂ laser. Absolute frequencies of the stronger lines were determined to ± 5.3\cdot10^-5cm^-1. Their intensities were determined to \approx10%. The dependence of the line width on pressure was determined. Comparison of our results with other experimental and theoretical results (J. Hillman et al.,1998) will be discussed.

V.Morozhenko acknowledges support under an NAS/NRC Resident Research Associateship.

References: [1] Kostiuk, T., {\it Infrared Phys.Technol.} {\bf 35}, 243, (1994). [2] Goldstein, J. J., M. J. Mumma, T. Kostiuk, D. Deming, F. Espenak, and D. Zipoy, \ {\it Icarus}, {\bf 94}, 45-63, (1991). [3] Kostiuk, T., R.Romani, F.Espenak, T.Livengood, J.J.Goldstein, {\it J.of Geophys. Research}, {\bf 98}, 18823 (1993). [4] Hillman, J.J., D.C.Reuter, J.M.Sirota, W.E.Blass, S.J.Daunt, L.R.Senesac, A.C.Ewing, L.W. Jennings, M.C.Weber, J.S.Hager, S.L.Mahan, A.Fayt, Laboratory Space Science Workshop, Boston, April 01-03 (1998).